I'm not sure if that's possible. if it is, you would have to completely wipe EVERYTHING on the iphone, this includes it's bootup. I'm sure it's possible though, do some googleing, it's just risky

Why would that be? Just use FAT32 or NTSC loading and no need to wipe it. Just make an extra folder.

Given that if you plug in your iPhone to your computer it shows up as a flash drive it should work.
(This means, if the only way to access files on an iPhone is with a special program it's not gonna work on a Wii)